1. Technical Field
The invention relates to a piston ring and to a method for the production thereof. The piston ring comprises a plastically deformable material and has at least one edge between a running face and a piston ring flank, compressive stresses being introduced into the edge between the running face and the piston ring flank by roller burnishing.
2. Related Art
Conventional piston rings tend to fracture on loading. Piston rings are loaded thermally and dynamically during engine operation. In particular, high combustion pressures in conjunction with the axial groove play result in the piston rings being able to twist in the piston ring groove of a piston. The greatest stresses occur on the lower or upper running edge in the ring back opposite the ring gap on the piston ring (at 180°). If these stresses become too great, one or more hairline or incipient cracks occur in the boundary zone. These hairline cracks become bigger over time, which ultimately results in ring fracture.
Conventional possibilities of counteracting ring fractures consist in increasing the strength of the material or increasing the thickness of the material used. In the case of edge fractures, the strength of the edge can be further increased by the use of an insert.
Furthermore, fatigue fractures proceeding from hairline cracks that have formed at the edge of a piston ring occur in piston rings that twist on loading.